The exemplary embodiments described herein relate to clay-based gel retarders, including related methods and compositions.
Water often undesirably accompanies the production of oil and gas from a well penetrating a subterranean formation. The unwanted production of water from hydrocarbon-producing wells can constitute a considerable technical problem and expense in oilfield operations because the water must be separated before the hydrocarbons can be refined or used. If the ratio of produced-water to produced-hydrocarbon becomes sufficiently large, the cost of separating the water and disposing of it can become a barrier to continued production. This can lead to abandonment of a well penetrating a subterranean formation, even when significant amounts of hydrocarbons remain therein.
One way in which the foregoing problems can be addressed is through conformance control treatments, whereby water-producing zones become fully or partially blocked to fluid flow. Conformance control treatments can involve introducing gellable treatment fluids into a subterranean formation where a gel can form by crosslinking a water-soluble polymer using a crosslinking agent. The gel-time and the gel strength are among the factors that can determine the effectiveness of a conformance control treatment. For example, if the gel-time is too short, introduction or placement of the gellable polymer system into a subterranean formation can prove problematic. Conversely, if the gel-time is too long, the gellable polymer system may not form a gel in the desired portion of the subterranean formation, or long waiting periods may be required before further operations can be carried out. In some instances, to control the gel-time, gel-time accelerators or gel-time retarders are used which are believed to function via chemical interactions with the components of the gellable polymer system.
In many instances, the chemicals in gel-time retarders remain with the gel and over time can hydrolyze the gel, thereby weakening the gel. This may lead to the gel breaking down and resumption of water production. Accordingly, the purity and value of the produced hydrocarbons is diminished, and another conformance control treatment may be needed, both of which increase the cost of hydrocarbon production.